Fusible apparatus for protecting automatic sprinklers



June 18, 1968 R. M. HODNETT 3,388,747

FUSIBLE APPARATUS FOR PROTECTING AUTOMATIC SPRINKLERS Filed April 8,1966 INVENTOR. ROBERT M. HODNETT ATTORNEY United States Patent 3,388,747FUSKBLE APPARATUS FOR PROTECTING AUTOMATIC SPRINKLERS Robert M. Hodnett,Providence, R.I., assignor to Grinnell Corporation, Providence, R.I., acorporation of Delaware Filed Apr. 8, 1966, Ser. No. 541,275 1 Claim.(Cl. 169-39) ABSTRACT OF THE DISCLOSURE For an upright fire protectionsprinkler head installed in a clean room a fusible solder cover whichencloses the sprinkler and has its open end fric.ionally engaged on abase, which forms with this base exterior surfaces relatively free ofcrevices and therefore easily wiped off during periodic cleanings andwhich melts before the sprinkler head is actuated by the heat from afire.

In recent years, as a result of increased requirements for exactingprecision, the assembling of complex components, such as are used in thespace program and pharmaceutical houses, has been carried out insuperclean and sterile rooms, often referred to as clean rooms.

To maintain a superclean atmosphere requires frequent, periodic,sterilization by wiping all of the surfaces in the room. To date most ofthe owners of such rooms have waived the placing of fire protectionsystems containing automatic sprinklers in the rooms because the headscontain so many irregular and varied surfaces and crevices that to cleanthe large number of heads normally required in such a room is an onerousand costly job.

In my copending application S.N. 529,731, filed Feb. 24, 1966, I havedescribed a means by which an automatic sprinkler system containingpendent sprinklers may be made highly suitable for use in clean rooms.Such pendent sprinkler systems are the type that are prevalent in amajority of clean rooms. Occasionally, however, a clean room may belocated in a building in such a manner that the only suitable automaticsprinkler protection which may be desired or obtained is one utilizingupright sprinkler heads. Generally, such a system cannot be concealedand therefore the clean room operator, in addition to cleaning thesprinklers, must put up with the added burden of cleaning the exposedpiping of such a system. Under normal circumstances the heads would beconsiderably more difiicult to clean than the piping. However, byplacing suitable smooth caps over the heads this tedious cleaningprocedure can be greatly simlified. The present invention makes itpossible to cover each head with such a cap; one that will fuse and beremoved, so as not to interfere with the proper actuation of thesprinkler in the event of a fire.

Unlike the construction used to protect pendent sprinklers the presentinvention cannot rely on the force of gravity alone to remove any moltensolder from the operative area of the sprinkler. Thus, to prevent anyclogging of the sprinkler or its deflector I have utilized the novelstructure hereafter described. In addition, this novel structure willalso overcome the problems relating to the prior art devices asdescribed in my aforementioned copending application S.N. 529,731.

Other advantages of the invention will become apparent by reference tothe following description and accompanying drawing which describe andshow, for illustrative purposes only, a preferred embodiment of theinvention.

In the drawing:

FIG. 1 is a side elevation view, partly in section, illustrating atypical upright sprinkler installation with my improved base plate andprotective cap combination;

FIG. 2 is a perspective view of the combination of FIG. 1 with a portioncut away for clarity of details;

FIG. 3 is an exploded perspective view of the combination of FIG. 2.

Referring now in greater detail to the drawing, 10 generally indicates afusible automatic sprinkler mounted on an exposed water pipe 12. Themounting is accomplished normally by placing a T-fitting 14 in the pipe12. Each sprinkler head has a threaded butt portion 16 which extendsinto the threaded opening 18 in the fitting 14.

About the butt portion 16 is a substantially flat circular base plate 20which has an outstanding peripheral ledge 22 extending about the outercircumference 21 of-the plate. For reasons which will be explainedhereafterthe outer circumference 21 is shown to be threaded. Through thecenter of the plate is a threaded hole 23 for engaging the threaded buttportion 16.

Each sprinkler 10 is provided with a thermally responsive element and aclosure construction 25 and 26 respectively, also, a deflector 15 toproperly disperse the discharge water emanating from the sprinkler. Thesprinkler 10 illustrated herein is sold under the name Duraspeed.However, other types of sprinklers may be used.

A protective closed cuplike cap 30 is placed over the sprinkler 10 andplate '20 with the rim portion 32 of the cap resting on the ledge 22. Arubber or rubber-like gasket ring 34 is preferably interposed betweenthe rim portion 32 and the threaded circumference 21 of the plate tohold the cap in place by frictional engagement. The circumference isthreaded to give increased frictional holding power and thus preventloss of the gasket ring should the cap 30 be removed. This increasedfrictional holding power can also be achieved by knurling or similarscoring. In fact, under some circumstances it may be desirable toeliminate the gasket ring and construct the plate and cap so that thecap is held in direct frictional engagement with the circumference 21.This would be particularly true where the sprinkler and cap combinationwould be located in an atmosphere of constant high ambient temperaturewhich might tend to make a gasket ring dry and brittle.

The protective cap 30 is composed of a fusible solder preferably cast toa uniform thickness. The outer surface of the cap is normally polishedto a smooth finish to enhance its appearance and the ease with which itcan be wiped clean.

Each entire sprinkler combination is assembled by first fastening thepipe 12 into a suitable fitting 14, making sure that the threadedopening 18 in the fitting is preferably oriented upwardly. The buttportion 16 of the sprinkler is then threaded through the opening 23 inplate 20 and into the threaded opening 18. It should be noted that theillustrated plate 20 contains a central depression 27 adjacent the hole23. This is to provide sufiicient clearance for a wrench so that a goodpurchase will be obtained on the base of the sprinkler when tighteningit into the fitting 14.

The plate 20 is then threaded downwardly into engagement with the top ofthe fitting 14.

At this time the gasket 34 is placed over the plate 20 to rest on ledge22. and firmly engage the threaded circumference 21. The cap 30 is thenplaced over the gasket 34 so that the two are in frictional engagement,and the rim 32 rests on ledge 22.

As has been stated, the cap is composed of cast solder of a generallyuniform thickness. A thickness of A has been found suitable. Unlike thecap described in my aforementioned copending application it has beenfound preferably in the present instance to use a solder which has amelting point lower than the rating of the sprinkler head which itcovers. For example, a solder cap suitable for use with a F. or a F.rated head is A solder containing: Bismuth-44.47%; lead22.6%; tin-8.3%;cadmium-5.3%; and indium-19.1% would have a 117 melting point.Naturally, a higher rated head could use a cap having a higher meltingpoint solder. One reason for this distinction is that an uprightsprinkler with its cap will have more exposed surface and be subject toa greater heat soaking action because of the opportunity available tothe heat to surround the upright construction. Thus, the sprinklerwithin the cap will generally be subject to a similar heat buildup atthe same rate as the cap. If the protected sprinkler were rated at atemperature lower than the cap it is likely that the sprinkler would gooff before the cap melted under most fire conditions. This is notnormally true of the pendent sprinkler construction as is brought out inmy copending application referred to above.

In operation, when subjected to heat from a fire the cap will melt at apredetermined temperature. Generally this melting action will be in theform of a general collapse of the solder about the sprinkler. Normally,as the temperature continues to rise most of the molten solder will run01? the deflector 15 and plate 20'. It is to be expected, however, thatsome solder may remain on these parts. Ultimately, when the temperaturereaches a sufficiently high point the closure construction 25, 26 willbe actuated, opening the sprinkler to water flow. Should any solder belocated so that it would obstruct the normal Water pattern the waterwill sweep this solder out of its path and be dispersed as the sprinklerdesign requires. After a fire the entire cap and :plate combination isreplaced when the sprinkler is replaced.

Occasionally, either in the course of cleaning or merely by carrying alarge object nearby, the cap 30 may be knocked loose from its engagementwith gasket 34 and ledge 22. Replacement is simple; merely requiringthat the cap be placed into engagement with ledge 22 and frictionalengagement with gasket 34.

It is thus clearly seen that the present construction assures that underthe influence of a fire the proper sequence of cap removal and sprinkleractuation to extinguish the fire will occur. This permits the use ofsprinklers where they normally would not be used.

The present disclosure has been made by way of example and it isunderstood that changes in details of construction and the combinationand arrangement of parts may be resorted to without departing from thespirit and scope of the invention as claimed below.

It is intended that suchterms of reference as upper, lower, downwardly,etc., in the claims below are intended merely as terms to relateportions of the claimed combination with one another and not as terms oflimitation as to the orientation of the combination.

I claim:

1. A combination comprising:

(I) a substantially horizontal water supply pipe,

(II) a'fire extinguishing sprinkler which:

(A) has abutt portion joined to said pipe,

(B) extends upwardly from said pi e,

(C) has a predetermined temperature rating for actuation,

(III) a base plate which:

(A) is between said pipe and said sprinkler,

(B) has a first portion of its periphery provided with frictionamplifying means,

' (C) has a second portion of its periphery provided with acircumferential flange which:

(1) is adjacent said first portion, (2) projects outward beyond saidfriction amplifying means, (IV) a fusible cap which:

(A) is substantially cylindrical,

(B) has a substantially uniform thickness,

(C) has a closed upper end,

(D) has an open lower end which:

(1) embraces said friction amplifying means, (2) rests on said flange,

(E) is composed of a solder which has a melting temperature less thansaid predetermined temperature rating.

References Cited UNITED STATES PATENTS 1,230,469 6/1917 Esty 169371,432,386 10/1922 Curney 169--37 2,531,790 11/1950 Rowley 169382,890,758 6/1959 Pfalzgrafi et al. 169--37 3,130,790- 4/1964 Hodgman169-40 3,178,879 4/1965 Nardin 277187 X ALLEN N. KNOWLES, PrimaryExaminer.

M. HENSON WOOD, ]R., Examiner. M. MAR, Assistant Examiner.

